Semiconductor device

ABSTRACT

To provide a semiconductor device capable of preventing the bowing of the substrate, and having a semiconductor layer of a III-V group compound of a nitride system with excellent crystallinity. 
     The semiconductor layer of the III-V group compound of the nitride system whose thickness is equal to or less than 8 μm, is provided onto a substrate made of sapphire. This reduces the bowing of the substrate due to differences in a thermal expansion coefficient and a lattice constant between the substrate and the semiconductor layer of the III-V group compound of the nitride system. An n-side contact layer forming the semiconductor layer of the III-V group of the nitride system has partially a lateral growth region made by growing in a lateral direction from a crystalline part of a seed crystal layer. In the lateral growth region, dislocation density restricts low, therefore, regions corresponding to the lateral growth region of each layer formed onto the n-side contact layer has excellent crystallinity.

RELATION APPLICATION DATA

The present application claims priority to Japanese Application No.P2000-010057 filed Jan. 13, 2000, which application is incorporatedherein by reference to the extent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device including asemiconductor layer made of a semiconductor of a III-V group compound ofa nitride system.

2. Description of the Related Art

The semiconductor of the III-V group compound of the nitride system suchas a GaN mixed crystal, a AlGaN mixed crystal or a GaInN mixed crystalis a direct transition semiconductor material, and at the same time, hasa characteristic in such that its forbidden band width spreads from 1.9eV to 6.2 eV. For this reason, these semiconductors of the III-V groupcompound of the nitride system can obtain light emission from a visiblerange to an ultra violet range, therefore, it is noteworthy for amaterial making a semiconductor light-emitting device such as asemiconductor laser diode (LD) or a laser emitting diode (LED). Inconnection with this, the semiconductor of the III-V group compound ofthe nitride system is focused attention as a material making an electrondevice because of its fast saturation electron speed and its largebreak-down field.

In general, the semiconductor device using the semiconductor of theIII-V group compound of the nitride system has a structure such thatlayers of the semiconductor of the III-V group compound of the nitridesystem grown with a MOCVD (Metal Organic Chemical Vapor Deposition)method and a MBE (Molecular Beam Epitaxy) method, are stackedsequentially. As for the substrate, generally, materials whose qualityis different from that of the semiconductor of the III-V group compoundof the nitride system are employed and a sapphire (Al₂O₃) substrate ismainly employed. Conventionally, in such a semiconductor device, a totalthickness of the semiconductor of the III-V group compound of thenitride system becomes thicker to obtain the semiconductor of the III-Vgroup compound of the nitride system with excellent crystallinity, whichmaintains and enhances electrical or optical device characteristics. Thesemiconductor of the III-V group compound of the nitride system withexcellent crystallinity can be obtained by growing under hightemperature (in case of GaN, the temperature is about 1000° C.).

However, sapphire and the semiconductor of the III-V group compound ofthe nitride system are different in a lattice constant and has a largedifference in a thermal expansion coefficient. For this reason, whengrowing the semiconductor of the III-V group compound of the nitridesystem, bowing of the sapphire substrate is caused. The bowing of thesapphire substrate is like to be larger when growing the semiconductorof the III-V group compound of the nitride system thicker or whengrowing under high temperature. The bowing of the substrate causesfractures in the sapphire substrate and the bowing of the semiconductorlayer of the III-V group compound of the nitride system, which fails instability in a manufacturing process significantly. In addition,temperature of the substrate when growing the semiconductor of the III-Vgroup compound of the nitride system becomes unstable, and then acomposition of the semiconductor of the III-V group compound of thenitride system grown thereon becomes heterogeneous depending ranges,which consequently gives damage to controllability in a manufacturingprocess. Specifically, when growing the GaInN mixed crystal as an activelayer of a light-emitting device using the semiconductor of the III-Vgroup compound of the nitride system, a taken-in-amount of indium (In)changes. As a result of this, variation in an oscillation wavelengthoccurs so that a light-emitting effective area capable of oscillating aspecific wavelength, becomes narrow.

Such problems can be solved by using a substrate made of thesemiconductor of the III-V group compound of the nitride system such asGaN. However, for using this kind of the substrate, there are problemsin that a manufacturing cost and a size of the substrate, then it hasnot been commercialized yet. Accordingly, in a recent situation, thebowing of the substrate is a problem to be solved urgently.

In recent years, as for growing a crystal of the semiconductor of theIII-V group compound of the nitride system, several technique to reducedensity of the penetration dislocation (a defect such that a dislocationdefect is propagated and penetrated in crystals; See FIGS. 5 and 9) aresuggested. One of the techniques is to form an opening such that atrench in a seed crystal of the semiconductor of the III-V groupcompound of the nitride system formed on the substrate, and then acrystal is grown in a lateral direction from a side wall surfacecorresponding to the opening of the seed crystal. As for othertechniques, there is a technique such that a belt-shaped mask is formedonto the semiconductor layer of the III-V group compound of the nitridesystem which becomes an underlying layer, and the semiconductor of theIII-V group compound of the nitride system is selectively grown in alateral direction thereon. With such techniques, it is desired that thesemiconductor of the III-V group compound of the nitride system withexcellent crystallinity is grown and device characteristics areenhanced. However, even if with these techniques, the above-mentionedbowing of the substrate is caused. Accordingly, reduction of the bowingof the substrate is urgent necessity for enhancing productivity anddevice characteristics.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

SUMMARY OF THE INVENTION

The invention has been achieved in consideration of the above problemsand its object is to provide a semiconductor device capable ofpreventing bowing the substrate and having a semiconductor layer of aIII-V group compound of a nitride system with excellent crystallinity.

A semiconductor device according to the present invention comprises asemiconductor layer made of a semiconductor of a III-V group compound ofa nitride system containing at least one kind element among a III groupelement and at least nitride among a V group element on one side of thesubstrate, and the semiconductor layer partly has a lateral growthregion made by growing the semiconductor of a III-V group compound of anitride system in a lateral direction, then a thickness of thesemiconductor layer is equal to or less than 8 μm.

In a semiconductor device according to the present invention, thesemiconductor layer having a lateral growth region is equal to or lessthan 8 μm, so that the semiconductor is excellent in crystallinity andat the same time, bowing of the substrate can be restricted.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description of the preferred embodimentsgiven with reference to the accompanying drawings, in which:

FIG. 1 is a section view showing a configuration of a main part of asemiconductor laser diode relative to a first embodiment of the presentinvention;

FIG. 2A is a section view for describing a method of manufacturing thesemiconductor laser diode shown in FIG. 1;

FIG. 2B is a section view for describing a method of manufacturing thesemiconductor laser diode following to FIG. 2A;

FIG. 2C is a section view for describing a method of manufacturing thesemiconductor laser diode following to FIG. 2B;

FIG. 3 is a section view for describing an advantage of appropriatelychoosing a width of a crystalline part and an opening part of thesemiconductor laser diode shown in FIG. 1;

FIG. 4 is a section view for describing manufacturing processesfollowing to FIG. 2C;

FIG. 5 is a diagram showing a part of the semiconductor laser diodeshown in FIG. 1;

FIG. 6 is a section view for describing manufacturing processesfollowing to FIG. 4;

FIG. 7 is a section view for describing manufacturing processesfollowing to FIG. 6;

FIG. 8 is a section view showing a configuration of a main part of asemiconductor laser diode relative to a second embodiment;

FIG. 9 is a diagram showing a part of the semiconductor laser diodeshown in FIG. 8;

FIG. 10 is a view showing a relationship between a half-breadth value ofa locking curb in an X-ray diffraction and a thickness of GaN layers ofthe semiconductor laser diode obtained by Examples 1-5 and Comparativeexamples 1-5 of the present invention;

FIG. 11 is a section view showing a configuration of a main part of asemiconductor laser diode relative to other modifications of thesemiconductor laser diode shown in FIG. 1;

FIG. 12 is a diagram showing a part of the semiconductor laser diodeshown in FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, embodiments of the present invention will be described byreferring drawings in detail.

FIG. 1 is a view showing a configuration of a main part of asemiconductor laser diode as a semiconductor device relative to a firstembodiment of the present invention. This semiconductor laser diode hasa structure on a substrate 11 such that a seed crystal layer 22, an-side contact layer 23, a n-side clad layer 24, a n-side guide layer25, an active layer 26, a p-type guide layer 27, a p-type clad layer 28and a p-side contact layer 29 are stacked as a semiconductor layer of aIII-V group compound of the nitride system 20 (herein after it isreferred to as a semiconductor layer 20) in this order with a bufferlayer, which is a part of the semiconductor layer 20, in between. Here,the semiconductor of the III-V group compound of the nitride systemcontains at least, one kind element among a III group element such asgallium (Ga), aluminum (Al), boron (B) or indium (In) and at leastnitride (N) among a V group element.

A p-side electrode 31 is formed onto the p-side contact layer 29. Then-side contact layer 23 partially has regions where the n-type cladlayer 24, the n-type guide layer 25, the active layer 26, the p-typeguide layer 27, the p-type clad layer 28 and the p-side contact layer 29are not formed thereon. An insulating layer 12 is provided with sides ofthe above-mentioned layers and surfaces of the p-type clad layer 24 andthe n-side contact layer 23. An n-side electrode 32 is provided onto then-side contact layer 23 with an opening 12 a provided in the insulatinglayer 12 in between.

The substrate 11 is made of a material whose thermal expansioncoefficient is different from that of the semiconductor layer 20, forexample, 80-μm-thickness sapphire. The buffer layer 21 and the like areformed onto a c face of the substrate 11. A concave part 11B is providedin a region corresponding to an opening part 22B of the seed crystallayer 22, which will be described later. A preferable depth of theconcave part 11B is equal to or more than 100 nm.

A total thickness of layers forming the semiconductor layer 20 is equalto or less than 8 μm, because such layers can reduce the bowing of thesubstrate 11 caused by differences in the thermal expansion coefficientor in a lattice constant between the substrate 11 and the semiconductorlayer 20. More preferably, the total thickness of the semiconductorlayer 20 is within a range between equal to or more than 4 μm and equalto or less than 8 μm. As for the reason of such thickness, if thicknessis less than 4 μm, element characteristics are degraded by poorcrystallinity.

Specifically, the buffer layer 21 is within a range of 0.01 μm to 0.05μm in a stacked direction (hereinafter it is referred to as athickness), and is made of undope-GaN. This buffer layer 21 is made of acrystal similar to amorphous, and is a core when growing thesemiconductor layer 20. Additionally, the buffer layer 21 has anaperture part 21B, which is provided in stripes with a predeterminedinterval of about from few μm to 10-odd μm. That is, in this case, acrystal of undope-GaN is also provided in stripes with a predeterminedinterval in between.

The seed crystal layer 22 is stacked onto the buffer layer 21, and has acrystalline part 22A made of a crystal of the semiconductor of the III-Vgroup compound of the nitride system and an opening part 22Bcorresponding to a concave part 11B of the buffer layer 21. A crystal ofundope-GaN whose thickness is within a range of 0.5 μm to 4.0 μm or acrystal of n-type GaN doped silicon (Si) as n-type impurity may be aspecific example of the crystalline part 22A. Here, the seed crystallayer 22 corresponds to one specific example of a first crystallinelayer of the invention. The opening part 22B corresponds to one specificexample of a trench part of the invention.

The n-side contact layer 23 is made of n-type GaN doped silicon asn-type impurity and partially has a lateral growth region by growing ina lateral direction from the crystalline part 22A of the seed crystallayer 22. A preferable thickness of the n-side contact layer 23 is equalto or less than 6.0 μm, because such thickness reduces the bowing of thesubstrate 11, much more, thermal distribution of the substrate 11 can bemore stable when stacking each of layers forming the semiconductor layer20. Here, the n-side contact layer 23 corresponds to a specific exampleof a second crystalline layer of the present invention.

The n-type clad layer 24 is, for example, within a range of 0.7 μm to1.2 μm and is made of an n-type AlGaN mixed crystal (for instance,Al_(0.08)Ga_(0.92)N) doped silicon as n-type impurity. The n-type guidelayer 25 is, for example, within a range of 0.08 μm to 0.12 μm and ismade of n-type GaN doped silicon as n-type impurity. The active layer 26is, for example, within a rage of 0.02 μm to 0.04 μm and has a multiplequantum well structure. This structure comprises a well layer and abarrier layer formed by a GaInN mixed crystal layer having differentcomposition respectively. respectively.

The p-type guide layer 27, is for example, within a range of 0.08 μm to0.12 μm and is made of p-type GaN doped magnesium (Mg) as p-typeimpurity. The p-type clad layer 28 is, for example, within a range of0.3 μm to 0.7 μm and is made of a p-type AlGaN mixed crystal dopedmagnesium as p-type impurity. The p-side contact layer 29 is, forexample, within a range of 0.05 μm to 0.1 μm and is made of p-type GaNdoped magnesium as p-type impurity. Here, for electric currentrestriction, a part of the p-side contact layer 29 and the p-type cladlayer 28 is formed in a narrow belt shape (so-called laser stripe; inFIG. 1, a belt shape extends in a vertical direction relative to a paperof FIG. 1). This laser stripe is provided in a range of the opening part22B of the seed crystal layer 22 thereon, for example.

The p-side electrode 31 is sequentially stacked palladium (Pd), platinum(Pt) and gold (Au) from a side of the p-side contact layer 29 and iselectrically connected to the p-side contact layer 29. On the otherhand, the n-side electrode 32 is sequentially stacked titanium (Ti),aluminum (Al), platinum (Pt), and gold (Au) and is electricallyconnected to the n-side contact layer 23.

In this semiconductor laser diode, for instance, a pair of sidesvertical to a longitudinal direction of the p-side electrode 31 is anend surface of a resonator. A pair of reflective mirrors (unillustrated)is respectively formed in the pair of an end surface of a resonator.

Next, a method of manufacturing the semiconductor laser diode will beexplained.

In the present embodiment, as shown in FIG. 2A, the substrate 11 whosethickness is about 430 μm and made of sapphire, is prepared. With theMOCVD method, the semiconductor layer 20 is grown onto the c face of thesubstrate 11 in order to become a thickness equal to or less than 8 μm.Specifically, the semiconductor layer 20 is grown as describedhereinafter.

First, a growth layer 21 a is grown in a range of 0.01 μm to 0.05 μm inorder to form the buffer layer 21. In this case, a temperature of thesubstrate 11 is set, for example, at 520° C. Then, the temperature iselevated at 1000° C. and undope-GaN or n-type GaN doped silicon is grownin a range of 0.5 μm to 4.0 μm onto the growth layer 21 a for a bufferlayer 21 so as to form a growth layer 22 a in order to form a seedcrystal layer 22. After this, for instance, with a CVD (Chemical VaporDeposition) method, the insulating film 41 made of silicon nitride orsilicon dioxide is formed on the growth layer 22 a for a seed crystallayer 22. The growth layer 22 a for a seed crystal layer 23 can beformed in each of atmospheres: an atmospheric atmosphere, a low-pressureatmosphere, a high-pressure atmosphere. However, among theseatmospheres, for obtaining a crystal with high quality, thehigh-pressure atmosphere is preferable.

Following this, as shown in FIG. 2B, a photoresist film 42 is formedonto a insulating film 41 and a plurality of striped patterns arrangedwith a predetermined interval is formed in <1-100> directions of a GaNcrystal (the growth layer 22 a for the seed crystal layer 22). Then, forexample, RIE is carried out with this photoresist film 42 as a mask inorder to remove the insulating film 41 selectively. The photoresist film42 is removed after removing the insulting film 41 selectively. Here,<1-100> represents by adding “-” in front of numerals for convenience inwriting, although it generally is represented by drawing a line overnumerals.

After removing the photoresist film 42, as shown in FIG. 2C, RIE iscarried out with the insulating film 41 as a mask in order to removeparts, which the growth layer 22 a, the growth layer 21 a and thesubstrate 11 are uncovered with the insulating film 41 to expose thesubstrate 11 in turn. This etching the growth layer 22 a into the seedcrystal layer 22 having the crystalline part 22A and the opening part22B, and turns the growth layer 21 a for a buffer layer into the bufferlayer 21 having the aperture part 21B. Additionally, the concave part11B is formed in the substrate 11.

As shown in FIG. 3, RIE is carried out in a preferable manner that alength L₁ in a width direction of the crystalline part 22A of the seedcrystal layer 22 (hereinafter it is referred to as a width) is less than4 μm, and a width L₂ of the opening part 22B is equal to or less than 12μm. Additionally, the width L₁ of the crystalline part 22A is preferablywithin a range of 2 μm to 4 μm and the width L₂ of the opening part 22Bis within a range of 8 μm to 12 μm. The range of 8 μm-12 μm includes 12μm. Specifically, the seed crystal layer 12 is formed in a manner thatthe width L₁ is 3 μm and the width L₂ is 9 μm.

In determining the width of L₂ of the opening part 22B being equal to orless than 12 μm, if the width L₂ is more than 12 μm, each of thecrystals grown in a lateral direction from a side wall surface of thecrystalline part 22A meets, which causes problems such that a growthsurface of the n-side contact layer 23 takes time to be flatten or aflat growth surface can not be obtained. Additionally, for the reason ofdetermining the width L₂ of the opening part 22B is more than 8 μm, theso-called laser stripe whose thickness is a range of 2 μm to 3 μm can beformed easily in a part of half of the width L₂ of the opening part 22B(a part of the width L₂/2 in FIG. 3).

On the other hand, determining the width of the crystal part 22A is lessthan 4 μm, if the width is more than 4 μm, a contact area of the seedcrystal layer 22 and the substrate 11 becomes larger, which leads thebowing of the substrate 11 caused by differences in the thermalexpansion coefficient and the lattice constant between materialscontained in the substrate such as sapphire and the semiconductor of theIII-V group compound of the nitride system. If the width of thecrystalline part 22A is less than 2 μm, the width is too narrow, whichcauses difficulties at production.

After exposing the substrate 11 selectively, as shown in FIG. 4, theinsulating 41 is removed by etching. Then, silicon is doped as n-typeimpurity from the crystalline part 22A of the seed crystal layer 22 togrow n-type GaN, which forms the n-side contact layer 23. Here, crystalgrowth of GaN mainly progresses from a top surface and a side wallsurface of the crystalline part 22A, and in case of regions except overthe crystalline part 22A, it progresses in a lateral direction (alateral growth region X). In addition, the crystal growth alsoprogresses in a lateral direction from a side wall surface of the bufferlayer 21. As shown in FIG. 5, this propagates penetration dislocation Mlfrom the seed crystal layer 22 (the crystalline part 22A) in a region Yover the crystalline part 22A of the n-side contact layer 23. However,in regions except the region Y (that is, the lateral growth region X),the penetration dislocation M₁ hardly exists because it bends in alateral direction. Growth speed from a side of the crystalline part 22Ais faster than that from a surface of the crystalline part 22A. After alapse of specific time, a crystal of GaN grown from the side of thecrystalline part 22A spreads over and the growth surface is flattened.The penetration dislocation M₂ shown in FIG. 5 is generated such thateach of crystals is grown from the crystalline part 22A and meets in alateral direction.

As described above, in case that the crystal growth progresses in alateral direction from the seed crystal layer 22 and the buffer layer21, it may slightly progress in a direction of a side of the substrate11, not to the just right. However, in the present embodiment, a part ofthe substrate 11 is etched to provide the concave part 11B, which canprevent a defect caused by contact of grown crystals to the substrate11. In addition, a crystal with less crystal disorientation, can begrown.

As has been described, crystals obtained by the above-mentioned methodcan gain a high quality compared with crystals obtained by otherchemical vapor deposition methods. Hence, in the present embodiment,even if a thickness of the semiconductor layer 20 becomes thinner, eachof layers except the buffer layer 21 comprising the semiconductor layer20 is excellent in crystallinity.

After forming the n-side contact layer 23, as shown in FIG. 6, on then-side contact layer 23, with the MOCVD method, for example, the n-typeclad layer 24 is grown in a range of 0.7 μm to 1.2 μm, the n-type guidelayer 25 is grown in a range of 0.08 μm to 0.12 μm, and then the activelayer 26 is grown in a range of 0.02 μm to 0.04 μm, further, the p-typeguide layer is grown in a range of 0.08 μm to 0.12 μm, the p-type cladlayer 28 is grown in a range of 0.3 μm to 0.7 μm, and finally, thep-side contact layer 29 is grown in a range of 0.05 m to 0.1 μm. Wheneach of layers is grown, a temperature of the substrate 11 is adjustedsuitably at about 750° C.-1100° C. respectively.

A total thickness of the buffer layer 21, the n-side contact layer 23,the n-type clad layer 24 and the n-type guide layer 25 is so thin thatthe bowing of the substrate 11 is restricted when the n-type guide layer25 is formed. Accordingly, when forming the active layer 26 made of aGaInN mixed crystal thereon, the temperature of the substrate 11 keepsstable, thus, a fixed amount of indium is taken in. Therefore,compositions of each of well layers in the active layer 26 andcompositions of each of barrier layers are homogeneous without change inevery region.

Additionally, the penetration dislocation M₁ is like to be propagatedslightly spreading in a radiant way in a growth direction of thesemiconductor layer 20. In the present embodiment, the total thicknessof the semiconductor layer 20 is equal to or less than 8 μm so that thespread of the above-mentioned penetration dislocation M₁ can be smallerthan conventional one.

When the MOCVD method is carried out, the gases described later areemployed respectively. Trimethylgallium ((CH₃)₃Ga) is employed as sourcegas for gallium. Trimethylaluminum ((CH₃)₃Al) is employed as source gasfor alminum. Trimethylindium ((CH₃)₃In) is employed as source gas forindium. Ammonia (NH₃) is employed as source gas for nitride. Inaddition, monosilane (SiH₄) is employed as source gas for silicon.Bis=cycropentadienyl magnesium ((C₅H₅)₂Mg) is employed as source gas formagnesium.

After growing the semiconductor layer 20, a part of the p-side contactlayer 29, the p-type clad layer 28, the p-type guide layer 27, theactive layer 26, the n-type guide layer 25, the n-type clad layer 24 andthe n-side contact layer 23 is etched in turn to expose the n-sidecontact layer 23 on a surface. Following this, an unillustrated mask isformed to be used for selectively etching a part of the p-side contactlayer 29 and the p-type clad layer 28 with RIE (a Reactive Ion Etchingmethod), and an upper part of the p-type clad layer 28 and the p-sidecontact layer 29 become a narrow belt shape (a ridge shape).

In this case, the unillustrated mask is preferably disposed in a regioncorresponding to the width L₂/2 shown in FIG. 3. Since penetrationdislocation M₂ is generated by meeting each of crystals grown in alateral direction from the crystalline part 12 and exists in the generalcenter of the width of the opening part 22B and, so-called laser stripewhich becomes a radiative range, is formed from a part of a boundarysurface of the opening part 12A and the crystalline part 22A to half ofthe width L₂ of the opening part 12B.

After this, as shown in FIG. 7, the insulating layer 12 made of silicondioxide (SiO₂) is formed with a deposition method in a whole exposedsurface. Then, an unillustrated resist film is formed thereon. With RIE,the insulating layer 12 is exposed by selectively removing a regioncorresponding to the above-mentioned ridge shape in the resist film.Following this, by removing the exposed surface of the insulating film12, the p-side contact layer 29 is exposed on a surface to cover regionsexcept the surface of the p-side contact layer 29 with the insulatinglayer 12.

The p-side electrode 31 is formed by depositing palladium, platinum, andgold in turn on a surface and in a vicinity of the p-side contact layer29. After forming the opening 12 a in a region on the n-side contactlayer of the insulating layer 12, the n-side electrode 32 is formed bydepositing titanium, aluminum, platinum and gold in turn to the opening12 a. Then, the substrate 11 is ground in a manner to be 80 μm ofthickness, for example. Here, the bowing of the substrate 11 isrestricted so that it is ground easily. Finally, the substrate 11 iscleaved in a predetermined width perpendicular to a longitudinaldirection of the p-side electrode 31, and on a cleavage surface, theunillustrated reflective mirrors are formed.

In the semiconductor laser diode, after a predetermined voltage isapplied to the p-side electrode 31 and the n-side electrode 32, thecurrent is applied to the active layer 26, which generates radiationcaused by an electron-hole combination. A composition of a GaInN mixedcrystal of each well layer and each barrier layer forming the activelayer 26 are so homogenous that an oscillation wavelength is uniform.

As described above, in the semiconductor laser diode relative to thepresent embodiment, the semiconductor layer 20 whose total thickness isequal to or less than 8 μm is provided, which achieves restriction ofthe bowing of the substrate 11 caused by differences in the thermalexpansion coefficient or the lattice constant between the substrate 11and the semiconductor layer 20. Additionally, the bowing of thesemiconductor layer 20 accompanying by the bowing of the substrate 11can also be restricted. Consequently, before and after manufacturing,this prevents fractures of the substrate 11 and the semiconductor layer20.

Further, accompanying by reduction of the bowing of the substrate, whengrowing the semiconductor layer 20, the temperature of the substrate 11becomes stable. Therefore, especially, when forming the active layer 26made of a GaInN mixed crystal, the fixed amount of indium taken in,thereby each of well layers and barrier layers comprising the activelayer 26 become homogeneous in composition. Hence, when activating, anoscillation wavelength becomes uniform, which attains a semiconductorlaser diode with high repeatability. In addition, a position of forminga radiative range is not limited and flexibility in production can beattained, which contributes to productivity.

Furthermore, the n-side contact layer 23 is formed by using thecrystalline part 22A and has the lateral growth region X so that then-side contact layer 23, the n-type clad layer 24, the n-type guidelayer 25, the active layer 26, the p-type guide layer 27, the p-typeclad layer 28 and the p-side contact layer 29, those layer are formed onthe n-side contact layer 23, have high crystallinity in the lateralgrowth region X. For the reason of this, if so-called laser stripe isformed in the lateral growth region X (specifically, a regioncorresponding to half of the width L₂ of the opening part 22B ),degradation caused by applying a voltage is hardly occurred, thereby,the semiconductor laser diode with long life can be obtained.

When manufacturing, a crystal of the semiconductor of the III-V groupcompound of the nitride system whose thickness is equal to or less than8 μm, is grown from the crystalline part 22A of the seed crystal layer22 having the opening part 22B. Therefore, in the lateral growth regionX, a high quality crystal in which the penetration dislocation M₁ hardlyexist, is grown, and even if the penetration dislocation M₁ slightlyspreads in a crystal growth direction, since a thickness of a growncrystal is not thick enough, the penetration dislocation M₁ affectsless. This increases an excellent region in crystallinity withlow-density of the penetration dislocation M₁, and in a latter process,a region capable of forming a radiative range increases. Flexibility inproduction can be enhanced, and the semiconductor laser diode with highquality and excellent repeatability can be obtained easily.

In connection with this, the bowing of the substrate 11 is restricted,which reduces a burden to the semiconductor layer 20 and as a result ofthis, manufacturing yields can be enhanced.

The semiconductor laser diode is utilized as a semiconductorlight-emitting apparatus by mounting on a heat sink through a submount.The heat sink is for dissipating heat generated by the semiconductorlaser diode. In the semiconductor laser diode of the present embodiment,as described above, the bowing of the submount 11 and accompanying bythis, the bowing of the semiconductor layer 20 are reduced. As a resultof this, the contact among the submount, the heat sink and thesemiconductor laser diode increases, then the heat generated by thesemiconductor laser diode when actuating can be dissipated well. Thiscan prevent an increase in threshold current of the semiconductor laserdiode and a decrease in a radiative output due to thermal interference.As a result of this, high quality can be maintained for a long time andthe long-life semiconductor laser diode can be achieved.

Second Embodiment

FIG. 8 is a view showing a configuration of a main part of asemiconductor laser diode as a semiconductor device relative to a secondembodiment of the present invention. The semiconductor laser diode hasthe same configuration, work and effect as the semiconductor laser diodeexcept in that a semiconductor layer of a III-V group compound of anitride system 60 (herein after it is referred to as a semiconductorlayer 60) is included in replace of the semiconductor layer 20 relativeto the first embodiment and further a mask part 64 is also included.Therefore, the same configurations has the same references and thedetailed explanation is omitted.

The semiconductor layer 60 has an underlying layer 61, a covered growthlayer 62 and an n-side contact layer 63 in place of the buffer layer 21,the seed crystal layer 22 and the n-side contact layer 23 of thesemiconductor layer 20 respectively. The total thickness of thesemiconductor layer 60 is equal to or less than 8 μm and a range ofequal to or more than 4 μm to equal to or less than 8 μm is preferableas the same as the first embodiment.

The underlying layer 61 is provided adjacent to the substrate 11 withina range of 0.5 μm to 2.0 μm and made of a crystal of undope-GaN.

The mask part 64 is provided onto the underlying layer 61 with 0.1 μm ofthickness and made of dielectrics such as silicon nitride (Si₃N₄) orsilicon dioxide. The mask part 64 is a plurality of masks disposed in apredetermined interval. The plurality of masks is extended in a beltshape vertical to a sheet in FIG. 9 with an opening in between. On themask part 64, the covered growth layer 62 is selectively grown in alateral direction (a direction vertical to a stacking direction), whichshields propagation of the penetration dislocation M₁ (See FIG. 8) fromthe underlying layer 61.

The covered growth layer 62 is within a range of 0.5 μm to 2.0 μm andmade of undope-GaN. The covered growth layer 62 selectively has thelateral growth region X (See FIG. 9) grown in a lateral direction usingthe mask part 64. The n-side contact layer 63 is within a range of 2.0μm to 5.0 μm and made of n-type GaN doped silicon as n-type impurity.

Next, a method of manufacturing of the semiconductor laser diode will bedescribed hereinafter.

First, the substrate 11 made of sapphire is prepared. With the MOCVDmethod, the buffer layer 21 made of undope-GaN and the underlying layer61 are grown in turn. In the underlying layer 61, the penetrationdislocation M₁ illustrated with a thin line as shown in FIG. 9,typically exists. FIG. 9 is a view showing a part of processes in amethod of manufacturing the semiconductor laser diode.

Following this, with a CVD (Chemical Vapor Deposition) method, a silicondioxide layer is formed onto the underlying layer 61. Then, anunillustrated resist film is covered on the silicon dioxide layer toform a plurality of parallel belt-shaped resist patterns withphotolithography. By using this, the silicon dioxide layer isselectively removed with etching to form the mask part 64.

With the MOCVD method, the covered growth layer 62 made of undope-GaN isgrown in the same manner as the underlying layer 61. At this moment,firstly, GaN is grown in a manner to fill openings in each mask of themask part 64 and is grown in a lateral direction on the mask.Accordingly, as shown in FIG. 9, in the region Y where the mask on theunderlying layer 61 is not formed among the covered growth layer 62, thepenetration M₁ is generated as the same as the underlying layer 61because the penetration dislocation M₁ is propagated from the underlyinggrowth layer 61. On the other hand, in the region X on the mask partwithin the covered growth layer 62, the penetration dislocation M₁ isgenerated because it is grown in a lateral direction.

After growing the covered growth layer 62, for example, with the MOCVDmethod, the n-side contact layer 63 is formed thereon. Processes afterthis are the same as the first embodiment. In the n-side contact layer63, the n-type clad layer 24, the n-type guide layer 25, the activelayer 26, the p-type guide layer 27, the p-type clad layer 28 and thep-side contact layer 29, the penetration dislocation M1 is notpropagated in a part corresponding to the lateral growth region X (FIG.9). Therefore, when the upper part of the p-type clad layer 28 and thep-side contact layer 29 are shaped in a ridge shape, if those layers areetched in a manner to leave the region Y (FIG. 9) on the mask part 64where the penetration dislocation M₁ is not propagated, devicecharacteristics of semiconductor laser diode such as lifecharacteristics can be enhanced since a low-density region of thepenetration dislocation M₁ (that is, a region with excellentcrystallinity) become a radiative range on the above-mentioned layers.

As described above, in the semiconductor laser diode relative to thepresent embodiment, the semiconductor layer 60 whose total thickness isequal to or less than 8 μm, is provided on the substrate 11 so that thebowing the substrate 11 can be restricted as the same as the firstembodiment.

Additionally, in a region on the mask part 64 formed on the underlyinglayer 61, the covered growth layer 62 is disposed. In the covered growthlayer 62, propagation of the penetration dislocation M₁ is effectivelyprevented from the underlying layer 61 with a lateral growth, so that asemiconductor of a III-V group compound of a nitride system withexcellent crystallinity is formed on the region (the lateral growthregion X) where the propagation of the penetration dislocation M₁ iseffectively prevented. Hence, device characteristics of thesemiconductor laser diode can be improved by disposing a radiative rangein a part corresponding to the lateral growth region X.

EXAMPLE

Further, specific examples of the present invention will be described indetail.

Examples 1-5; Evaluation of the GaN Layer

First, a substrate made of sapphire was prepared. GaN was grown on a cface of the substrate 40 nm with a MOCVD method to form a growth layerfor a buffer layer. Following this, with the same MOCVD method, GaN wasgrown 2 μm to form a growth layer for a seed crystal layer, and then, ainsulating film made of silicon nitride was formed on the growth layerfor a seed crystal layer with a CVD method.

Next, a photoresist film was formed on the insulating film and at thesame time, a plurality of patterns with a striped shape was formed. RIEwas carried out with the pattern-formed photoresist film as a mask toremove the insulating film selectively. After this, the photoresist filmwas removed.

After removing the photoresist film, RIE was carried out with theinsulating film as a mask to remove part, which the growth layer for theseed crystal layer, the growth layer for a buffer layer, and thesubstrate were uncovered with the insulating film in turn. Then, thesubstrate was exposed to an interface between the substrate and thegrowth layer for a buffer layer. This formed a seed crystal layer havinga crystalline part and an opening part, and a buffer layer having anaperture part.

Following this, the insulating film was removed by etching. With theMOCVD method, a GaN layer was formed by growing GaN from the crystallinepart of the seed crystal layer. At this moment, in Examples 1-5, athickness of the GaN layer was changed as shown in Table 1. In addition,GaN grown from the crystalline part of the seed crystal layer had aregion grown in a lateral direction selectively.

TABLE 1 Thickness of GaN Half-Value Breadth (μm) (arcsec) Example 1 4.0158 Example 2 5.0 124 Example 3 5.0 131 Example 4 7.0 121 Example 5 8.0139 Comparative Example 1 10.0  194

When forming each of layers with the MOCVD method, trimethylgallium wasemployed as a source gas of gallium and ammonia was employed as a sourcegas of nitride.

As Comparative example 1 relative to Examples 1-5, the GaN layer wasgrown in a similar manner as Example 1-5 except in that a thickness ofthe GaN layer was 10 μm. As Comparative examples 2-5 relative toExamples 1-5, the GaN layer was grown as described hereinafter.

The substrate made of sapphire was prepared. GaN was grown 40 nm on thec face of the substrate with the MOCVD method to form the buffer layer.After this, on the buffer layer, GaN was grown with the MOCVD method toform the GaN layer. In this case, a thickness of the GaN layer waschanged as shown in Comparative examples 2-5. The GaN layer was grown ina vertical direction relative to a growth surface substantially.

TABLE 2 Thickness of GaN Half-Value Breadth (μm) (arcsec) ComparativeExample 2 3.9 222 Comparative Example 3 4.0 215 Comparative Example 44.0 227 Comparative Example 5 5.0 198

The obtained GaN layers as described above in Examples 1-5 andComparative examples 1-5 were analyzed with an X-ray diffraction method.FIG. 10 is a graph showing a half-value breadth of a locking curve withan X-ray analysis of the obtained GaN layers in Examples 1-5 andComparative examples 1-5. The obtained results are also shown in Tables1 and 2. In FIG. 9, a vertical axis shows a half-value breadth (unit;arcsec), and a horizontal axis shows a thickness of the GaN layer (unit;μm).

As can be seen in FIG. 10, Tables 1 and 2, a half-value breadth ofExample 1 was a smallest value in those of Comparative examples 2-4. Ahalf-value breadth of Example 2 was smaller than that of Comparativeexample 5. As a result of this, it was confirmed that GaN having aregion grown in a lateral direction was excellent in crystallinity.Further, any half-value breadths of Examples 1-5 were smaller than thatof Comparative example 1. This might be caused by the reason that if athickness of the GaN layer was 10 μm, the bowing of the substrateincreased, which caused an increase of deflection in crystals. As aresult described above, in the GaN layer whose thickness was equal to orless than 8 μm and grown in a lateral direction partly, the bowing ofthe substrate was reduced and excellent crystallinity could be achieved.

Although the detailed describe is omitted here, in case that asemiconductor of a III-V group compound of a nitride system containingat least one kind element among a III group element and nitrideexcluding GaN, is grown, the same results can be obtained.

Example 2; Evaluation of the Semiconductor Laser Diode

Further, with the MOCVD method, a n-type clad layer, a n-type guidelayer, an active layer, a p-type guide layer, a p-type clad layer and ap-side contact layer were formed onto the GaN layer of Example 2sequentialy. Specifically, an n-type Al_(0.08)Ga_(0.92)N mixed crystaldoped silicon was grown 1.2 μm to form the n-type clad layer and n-typeGaN doped silicon is grown 0.1 μm to form the n-type guide layer. Theactive layer was formed as described hereinafter. First, an N-type GaInNmixed crystal doped silicon is grown 7.0 nm to form the barrier layer,then, an undope-GaInN mixed crystal was grown 3.5 nm to form a welllayer. Finally, the active layer was formed by stacking those layers in3 periods. P-type GaN doped magnesium was grown 0.1 μm to form thep-type guide layer. A p-type Al_(0.08)Ga_(0.92)N mixed crystal was grownin 0.5 μm to form the p-type clad layer. P-type GaN doped magnesium wasgrown 0.1 μm to form the p-side contact layer.

When forming each of layers with the MOCVD method, trimethylgallium wasemployed as a source gas of gallium, trimethylaluminum was employed as asource gas of aluminum, trimethylinduim was employed as a source gas ofindium, and ammonia is employed as a source gas of nitride. Monosilanewas employed as a source gas of silicon, and bis=cycropentadienylmagnesium was employed as a source gas of magnesium.

After forming the p-side contact layer, the p-side contact layer, thep-type clad layer, the p-type guide layer, the active layer, the n-typeguide layer, the n-type clad layer and the n-side contact layer wereselectively etched to expose the n-side contact layer on a surface.Following this, a mask was formed parallel to a longitudinal directionof a region where a p-side electrode to be formed in a latter process.With a RIE method by using the mask, a part of the p-side contact layerand the p-type clad layer were selectively etched to shape the upperpart of the p-type clad layer and the p-side contact layer in a narrowbelt shape.

An insulating layer made of silicon dioxide was formed on the wholeexposed surface of the substrate with a deposition method. A resist filmwas formed thereon. Then, RIE was carried out in several times to coverregions except a surface of the p-side contact layer with the insulatingfilm.

After this, on a surface and in a vicinity of the p-side contact layer,palladium, platinum and gold were deposited sequentially to form thep-side electrode. An opening was formed in a region on the n-sidecontact layer of the insulating layer and titanium, aluminum, platinum,and gold were deposited thereon to form the n-side electrode. Afterthis, the substrate was ground in a manner to be 80 μm of thickness.Finally, the substrate was cleaved vertical to a longitudinal directionof the p-side electrode in a predetermined width, then, a reflectivemirror film was formed onto the cleavage surface to produce thesemiconductor laser diode. As for the above-mentioned Comparativeexample 5, the semiconductor laser diode was also produced as the sameas Example 2.

Further, a submount and a heat sink were prepared. The semiconductorlaser diodes of Example 2 and of Comparative example 5 were mounted onthe heat sink through the submount to assemble a semiconductorlaser-light emitting device, and then a life test was carried out atroom temperature. Consequently, the semiconductor laser diode of Example2 could achieve a life for over 1000 hours under 20 mW output. Ascompared with this, the semiconductor laser diode of Comparative example5 obtained a life for over 100 hours under 20 mW. This could be achievedfor the reason that the bowing of the submount was reduced, andaccompanying by this, the bowing of each layers made of thesemiconductor of the III-V group compound of the nitride system wasreduced. Hence, this enhanced a contact among the submount, the heatsink and the semiconductor laser diode, which results in effectivelydissipating heat generated by the semiconductor laser diode.

As has been described above, the present invention has been explained bygiven the embodiments and examples. The present invention is not limitedby the embodiments and the examples, and many modifications andvariations of the present invention are possible. For instance, in theabove-mentioned each of embodiments, although the contact layer and theguide layer were made of GaN, the clad layer was made of AlGaN mixedcrystal, and the active layer was made of InGaN mixed crystal, thesesemiconductor layers of the III-V group compound of the nitride systemmay be made of at least one kind element among a III group element andother semiconductors of a III-V group compound containing nitride. Inthe second embodiment, the underlying layer 61 made of undope-GaN andthe covered growth layer 62 was given as an example, and in the thirdembodiment, the seed crystal layer 71 made of undope-GaN was given as anexample, these layers also may be made of the semiconductor of the III-Vgroup compound of the nitride system excluding undope-GaN.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

Furthermore, although in the above-mentioned each of embodiments, thesubstrate 11 was made of sapphire, the substrate may be made ofmaterials whose thermal expansion coefficient is different from that ofthe semiconductor of the III-V group compound of the nitride system.Such materials are: silicon carbide (SiC) and spinel (MgAl₂O₄).

Moreover, in the above-mentioned first embodiment, after removing theinsulating 41, the n-side contact layer 23 was formed. As shown in FIG.11, the n-side contact layer 23 may be formed without removing theinsulating layer 41 on the seed crystal layer 22. This shields thepenetration dislocation M₁ with the insulating film 41, which preventspropagation of the penetration dislocation M₁ from the seed crystallayer 22. Accordingly, in the n-type contact layer 23, crystal defectshardly exist except the penetration dislocation M₂, which is a cause ofa meet. This can gain the semiconductor layer of the III-V groupcompound of the nitride system with excellent crystallinity. However,preferably, a manufacturing method may be chosen depending on a purposefor use because when growing the n-side contact layer 23, a materialscontained the insulating film 41 is mixed into the n-side contact layer23 as an impurity, which degrades characteristics of a semiconductorlaser diode.

In the above-mentioned each of embodiments, although it is describedthat the case where the semiconductor layer 20 and 60 were formed withthe MOCVD method, other chemical vapor deposition methods such as a MBEmethod and a HVPE (hideride chemical vapor deposition) method can beused to form these layers. The HVPE method is a chemical vapordeposition method such that halogen contributes to transportation orreaction.

In the above-mentioned each of embodiments, although the n-side contactlayer 23, the n-type clad layer 24, the n-type guide layer 25, theactive layer 26, the p-type guide layer 27, the p-type clad layer 28 andthe p-side contact layer 29 were sequentially stacked, a semiconductorlaser diode having other configurations can be applied to the presentinvention. For example, a degradation-preventing layer may be includedbetween the active layer 26 and the p-type guide layer 27 instead of then-type guide layer 25 and the p-type guide layer 27. Further, in theabove-mentioned each of embodiments, although a part of the p-type cladlayer 28 and the p-side contact layer 29 were shaped in a narrow beltshape for electric current restriction, other configurations may beapplied for electric current restriction. Additionally, although thesemiconductor laser diode of a ridge waveguide type combined with a gainwaveguide type and a reflective intensity waveguide type was describedas an example, a semiconductor laser diode of a gain wave guide type andthe semiconductor laser diode of a reflective intensity waveguide typecan be also applied in a like manner.

In the above-mentioned first embodiment, although it is described thatthe case where the concave part 11B was provided in the substrate 11,the concave part 11B is not always needed to provide. However, if theconcave part 11B is provided, occurrence of defects when producing anddislocation of a crystal axis can be prevented.

In addition, in the above-mentioned each of embodiments, although thesemiconductor laser diode was given as a semiconductor device, thepresent invention can be applied to other semiconductor devices such asa light-emitting diode or an electric field effect transistor.

As has been mentioned above, in the semiconductor device according tothe present invention, the lateral growth region is provided on thesubstrate and the semiconductor layer whose thickness is equal or lessthan 8 μm is disposed, so that even if the substrate and thesemiconductor layer has different quality of materials, the bowing ofthe substrate can be restricted, and the semiconductor layer made of thesemiconductor of the III-V group compound of the nitride can achievehigh crystallinity.

While the invention has been described with reference to specificembodiment chosen for purpose of illustration, it should be apparentthat numerous modifications could be made there to by those skilled inthe art without departing from the basic concept and scope of theinvention.

What is claimed is:
 1. A semiconductor device including a semiconductorlayer made of a semiconductor of a III-V group compound of a nitridesystem containing at least one element among a III group element and atleast nitride among a V group element on one side of the substrate,comprising; the semiconductor layer, which has partly a lateral growthregion made by growing the semiconductor of the III-V group compound ofthe nitride system, and whose thickness is not greater than 8 micrometerwherein the thickness prevents bowing of the substrate.
 2. Thesemiconductor device according to claim 1, further comprising a firstcrystal layer including a crystalline part made of a crystal of thesemiconductor of a III-V group compound of the nitride system and atrench and a second crystal layer made of the semiconductor of the III-Vgroup of the nitride system is disposed to cover the crystalline part ofthe first crystal layer.
 3. A semiconductor device, comprising: asubstrate; and a semiconductor nitride system made of a III-V groupcompound of a nitride system containing at least one element of a IIIgroup element and at least one nitride of a V group element, thesemiconductor nitride system including a first crystalline layer havinga seed crystal layer, the seed crystal layer having a first crystallinepart with a first length L1, the seed crystal layer further having anopening part with a second length, the second length L2 being longerthan the first length L1, the semiconductor nitride system furtherincluding a second crystalline layer having an n-side contact layer, thefirst crystalline layer and the second crystalline layer forming athickness not greater than 8 micrometer wherein the thickness preventsbowing of the substrate.
 4. The semiconductor device of claim 3, whereinthe thickness of the semiconductor nitride system is not less than 4micrometer and not greater than 8 m.
 5. The semiconductor device ofclaim 3, wherein the first length L1 is not greater than 4 micrometer.6. The semiconductor device of claim 3, wherein first length L1 is notless than 2 m and not greater than 4 micrometer.
 7. The semiconductordevice of claim 3, wherein first length L1 is 3 micrometer.
 8. Thesemiconductor device of claim 3, wherein the second length L2 is notgreater than 12 micrometer.
 9. The semiconductor device of claim 3,wherein the second length is not less than 8 m and not greater than 12micrometer.
 10. The semiconductor device of claim 3, wherein the secondlength L2 is 9 m.
 11. The semiconductor device of claim 3, wherein theopening part further includes a concave part.
 12. The semiconductordevice of claim 9, wherein the concave part is not less than 100 nm. 13.The semiconductor device of claim 3, wherein the n-side contact layer isnot greater than 6 micrometer.
 14. A semiconductor device made of aIII-V group compound of a nitride system containing at least one elementof a III group element and at least one nitride of a V group elementformed on a substrate, comprising: a first crystalline layer having aseed crystal layer, the seed crystal layer having a first crystallinepart with a first length L1 not being greater than 4 micrometer, theseed crystal layer further having an opening part with a second lengthL2 not being greater than 12 micrometer, the first length L1 and thesecond length L2 being sized to limit contact area between the seedcrystal layer and the substrate; and a second crystalline layer havingan n-side contact layer, the n-side contact layer being not greater than6 micrometer, the n-side contact layer being sized to stabilize thermaldistribution of the substrate, wherein the first crystalline layer andthe second crystalline layer form a thickness not greater than 8micrometer wherein the thickness prevents bowing of the substrate. 15.The semiconductor device of claim 14, wherein the first length L1 is 3micrometer.
 16. The semiconductor device of claim 14, wherein the secondlength L2 is 9 micrometer.
 17. A method of manufacturing a semiconductordevice to prevent bowing of a substrate, comprising the steps of:forming a seed crystal layer; etching a crystalline part into the seedcrystal layer, the crystalline part having a first length L1 not greaterthan 4 micrometer; etching an opening part into the seed crystal layer,the opening part having a second length L2 not greater than 12micrometer; and etching an n-side contact layer, the n-side contactlayer being not greater than 6 m wherein the sizing of the first lengthL1, the second length L2 and the n-side contact layer prevents bowing ofthe substrate caused by differences in the thermal expansion coefficientbetween the substrate and the seed crystal layer.
 18. The methodaccording to claim 17, wherein the sizing of the first length L1, thesecond length L2 and the n-side contact layer prevents bowing of thesubstrate caused by differences in the lattice constant between thesubstrate and the seed crystal layer.
 19. The method according to claim17, further comprising etching a concave part in the opening part. 20.The methoc according to claim 17, further comprising limiting thethermal distribution of the substrate.